1. Field of the Invention
The present invention relates to an ultrasonic imaging method and an ultrasonic imaging apparatus for transmitting and receiving ultrasonic waves to obtain images for ultrasonic diagnosis and so on.
2. Description of a Related Art
Ultrasonic waves reflect at a site where the acoustic characteristic impedance varies, i.e., at an interface between different media. Ultrasonic images are constructed in the form of images on the basis of internal information on an object to be inspected such as a living body obtained by utilizing the above-mentioned nature of the ultrasonic waves. More specifically, the internal information of the object such as the living body is obtained by transmitting ultrasonic waves from a probe containing a plurality of ultrasonic transducers to the object and receiving the ultrasonic waves reflected from a reflector existing in the interior of the object. Such internal information is iteratively collected while changing the direction in which the ultrasonic waves are transmitted, which enables shapes and motions of the internal organs, etc., within the living body to be constructed as images. Therefore, such ultrasonic diagnosis may be an effective diagnostic method for diseases causing pathological change which can be recognized in terms of the shapes and motions of the internal organs, etc.
By the way, acoustic characteristics of various tissues in the living body are becoming apparent little by little. For example, tissues containing more collagen as intercellular substance have a higher ultrasonic velocity and a greater attenuation value, whereas tissues having a higher water content have a smaller attenuation constant. However, such specific correlation between the acoustic characteristics and various tissues within the living body has not yet fully been elucidated. For example, in tissues like pathologically changed tissues of myocardial infarction where intermingled denatured portions having an increased water content in place of melted protein, fiberized portions containing collagen as an ingredient created for restoring the denatured portions, and sound myocardial portions are intermingled, a multiplicity of strong echo sources may be present because the acoustic impedance is significantly different among the respective tissues. For this reason, the pathologically changed tissues are displayed with a higher brightness in the ultrasonic images. On the contrary, in the case of pathologically changed tissues, etc. where a part or a whole of an internal organ has uniformly varied, such strong echo sources are not present and hence the difference in properties of the tissues may not necessarily be judged by the ultrasonic images.
In view of the above point, an object of the present invention is to provide an ultrasonic imaging method and an ultrasonic imaging apparatus capable of displaying not merely the shapes of internal organs, etc., but also the difference in properties thereof in the ultrasonic diagnosis.
In order to solve the above problems, according to one aspect of the present invention, there is provided an ultrasonic imaging method comprising the steps of: (a) obtaining plural kinds of image data by transmitting plural kinds of ultrasonic waves at different transmission power and receiving the plural kinds of ultrasonic waves reflected from an object to be inspected; and (b) performing arithmetic by using the plural kinds of image data obtained at step (a) to thereby figure out new image data.
According to one aspect of the present invention, there is provided an ultrasonic imaging apparatus comprising: ultrasonic wave transmission/reception means having a plurality of ultrasonic transducers, for transmitting ultrasonic waves toward an object to be inspected and receiving the ultrasonic waves reflected from the object to output a detection signal; signal processing means for generating image data on the basis of the detection signal output from the ultrasonic wave transmission/reception means; control means for controlling the ultrasonic wave transmission/reception means to vary transmission power of the ultrasonic waves to be transmitted so as to transmit and receive plural kinds of ultrasonic waves at different transmission power; storage means for accumulating image data output from the signal processing means to thereby store plural kinds of image data obtained by transmitting and receiving plural kinds of ultrasonic waves at different transmission power; and arithmetic means for performing arithmetic by using the plural kinds of image data stored in the storage means to thereby figure out new image data.
According to the present invention, plural kinds of ultrasonic images obtained by transmitting and receiving plural kinds of ultrasonic waves at different transmission power are combined, so that tissues different in properties within the interior of the object can be extracted and displayed.